21. Transformed Keratinocyte Colonies in Serum-Free Primary Culture of Epidermal Cell Suspension from UVB Induced Pigmented Spots in Mice

Tomohisa Hirobe

Keywords: melanoblast, melanocyte, heratinocyte, UVB, proliferation, differentiatton

Long-term exposure to ultraviolet radiation B (UVB) induced pigmented spots in the dorsal skin of hairless mice. To clarify the cellular mechanism for the development of these UVB-induced pigmented spots, epidermal cell suspensions from the dorsal skin of hairless mice at 37 weeks (the stage of devel opment of medium-sized pigmented spots) after the cessation of 8-week UVB exposures were cultured in a serum-free medium supplemented with dibutyryl adenosine 3':5'-cyclic monophosphate (DBcAMP) and basic fibroblast growth factor (bFGF). After 14 days, most of the keratinocytes had died and pure cultures of melanoblasts and melanocytes were obtained. However, when the culturing of melanoblasts and melanocytes was continued further, numerous transformed keratinocyte colonies (3-20/35 mm dish) were observed after 20 days. It may be assumed that a small number of keratinocytes remained in the dishes, and they were initiated to proliferate dramatically. Around the colonies, numerous melanoblasts and melanocytes were observed and some of them were in mitotic division. On the other hand, no transformed keratiocyte colonies were observed in control culture. These results suggest the possibility that the increase in the number of melanocytes observed in pigmented spots is caused by the changes brought about by the transformation of keratinocytes.

Publication:
Hirobe, T. and Abe, H.: Pigment Cell Res., 12, 147 163, 1999.